An image of a subject which a person sights is confirmed as a vision so that light of the subject to be incident to a cornea is refracted by the cornea and an eye lens to enter a vitreous body and it is focused on a retina which exists on aback surface side of the vitreous body, thereby sending the focused visual information to cerebrum via optic nerve. In this moment, when the light of the subject is focused on a position in front of or behind the retina, myopia or hyperopia occurs. Further, when the cornea or the eye lens is distorted, it is not focused on the retina, which causes the astigmatism.
As means for correcting such myopia, hyperopia, astigmatism and the like, a correction by a pair of glasses, a correction by a contact lens or the like has been widely performed. Further, for a correction of presbyopia, bifocal glasses (bifocal lens) or the like in which there are a portion for far viewing and a portion for close viewing in one lens have been utilized.
Additionally, as a technology for correcting the presbyopia securely, a mask configured to be implanted in a cornea of a patient has been proposed, which includes an anterior surface that resides adjacent a first corneal layer, a posterior surface that resides adjacent a second corneal layer, a plurality of holes extending at least partially between the anterior surface and the posterior surface, an aperture configured to transmit along an optic axis substantially all incident light and a substantially opaque portion surrounding at least a portion of the aperture (see a patent document 1 followed).